1. Field of the Invention
This invention generally relates to a torque distributing mechanism in a differential including a single input element and two output elements for distributing torque applied to the input element of the differential to the two output elements at a predetermined proportion.
2. Description of the Prior Art
A differential in a power transmitting system of an automobile is constructed such that a difference in rotational speed developed between left and right wheels, during turning of the automobile, is absorbed, and torque of an engine is distributed to the left and right wheels at an appropriate proportion. However, a common differential is operated by difference between loads applied to the left and right wheels. Therefore, such differential is accompanied by a problem that if one of the wheels gets on a road surface of small friction coefficient and slips, the amount of torque transmitted to the other wheel may be reduced, or transmission of torque may be cut off.
In order to solve the above problem, there is a conventionally-proposed torque distributing mechanism in a differential, designed to positively control the differential on the basis of rotational angle of a steering wheel and vehicle speed to distribute torque suitable for the current operational condition to left and right wheels.
FIG. 7 illustrates the structure of such prior art torque distributing mechanism in the differential. Referring to FIG. 7, propeller shaft 01, connected to an engine E and transmission M and driven thereby, is connected to central shaft 04 through bevel gear 02 and bevel gear 03. Right shaft 5.sub.R for driving right wheel W.sub.R and left shaft 5.sub.L for driving left wheel W.sub.L are coaxially disposed on laterally opposite sides of central shaft 04. Right differential D.sub.R is positioned between central shaft 04 and right shaft 5.sub.R, and left differential D.sub.L is positioned between central shaft 04 and left shaft 5.sub.L.
Both of differentials D.sub.R and D.sub.L are planetary gear types and comprised of planetary carriers 6.sub.R and 6.sub.L secured to right and left shafts 5.sub.R and 5.sub.L, respectively, planetary gears 7.sub.R and 7.sub.L rotatably carried on planetary carrier 6.sub.R and 6.sub.L, respectively, a pair of right and left sun gears 8.sub.R and 8.sub.L secured to central shaft 04 and meshed with planetary gears 7.sub.R and 7.sub.L, respectively, and a pair of right and left ring gears 9.sub.R and 9.sub.L meshed with planetary gears 7.sub.R and 7.sub.L, respectively. A pair of left and right bevel gears 10.sub.R and 10.sub.L formed, integrally, with right and left ring gears 9.sub.R and 9.sub.L are meshed with common bevel gear 013 driven through reducer 012 by motor 011.
With the torque distributing mechanism having the above structure, when torque transmitted to central shaft 04 is transmitted equally to right and left wheels W.sub.R and W.sub.L through differentials D.sub.R and D.sub.L, right and left ring gears 9.sub.R and 9.sub.L, i.e., right and left bevel gears 10.sub.R and 10.sub.L are not rotated. If a difference is developed between loads applied to right and left wheels W.sub.R and W.sub.L, however, a difference in rotational speed is intended to be developed between right and left shafts 5.sub.R and 5.sub.L, with the result that a difference in rotational speed is also developed between right and left ring gears 9.sub.R and 9.sub.L. Therefore, if a difference in rotational speed is positively provided to right and left bevel gears 10.sub.R and 10.sub.L, i.e., to right and left ring gears 9.sub.R and 9.sub.L through common bevel gear 013 by motor 011, the proportion of distribution of torque transmitted from central shaft 04 to right and left shafts 5.sub.R and 5.sub.L can be controlled.
In the above prior art torque distributing mechanism, however, the pair of right and left bevel gears 10.sub.R and 10.sub.L for providing a difference in rotational speed to right and left ring gears 9.sub.R and 9.sub.L and common bevel gear 013 meshed with the pair of right and left bevel gears 10.sub.R and 10.sub.L are indispensable. This results in a problem of increase in axial size of the torque distributing mechanism.